In an online chat from the White House with Google+ and YouTube users, Obama acknowledged that many of the drone strikes are in Pakistan's tribal regions near the Afghan border.
Obama said attacking Al-Qaeda or Taliban militants in Pakistan another way would involve "probably a lot more intrusive military action than the ones we're already engaging in."
??"I want to make sure the people understand actually drones have not caused a huge number of civilian casualties," Obama said. "For the most part, they have been very precise precision strikes against Al-Qaeda and their affiliates. And we are very careful in terms of how it's been applied.
"I think that there's this perception somehow that we're just sending in a whole bunch of strikes willy-nilly," he continued. "This is a targeted, focused effort at people who are on a list of active terrorists who are trying to go in and harm Americans, hit American facilities and American bases and so on."
Pakistan on January 31 acknowledged "tactical advantages" to U.S. drone strikes, but appeared to shrug off the unexpected confirmation by Obama of attacks on its soil.
Pakistan's Foreign Ministry spokesman Abdul Basit told France's AFP news agency: "Notwithstanding tactical advantages of drone strikes, we are of the firm view that these are unlawful, counterproductive, and hence unacceptable."
U.S. diplomatic cables leaked by WikiLeaks in late 2010 showed Pakistan's civilian and military leaders privately supported U.S. drone attacks, despite their public condemnation of the practice.
Pakistan's military support for drone strikes has included the sharing of intelligence needed to target Al-Qaeda militants within Pakistani territory.
Pakistan was allowing the United States to use its Shamsi air base in western Pakistan to refuel drone aircraft. According to some accounts, Shamsi was a hub for the CIA drone aircraft program.
But Islamabad ordered U.S. military personnel to leave Shamsi in 2011 amid deteriorating relations over the covert U.S. raid that killed Al-Qaeda leader Osama bin Laden in May.
Pakistani officials say Islamabad is now reviewing its alliance with the United States, and Pakistan has kept its Afghan border closed to NATO supply convoys since November 26.
According to unofficial media tallies, 45 suspected U.S. drone strikes were reported in Pakistan's tribal belt in 2009, 101 in 2010, and 64 in 2011.
David Rohde, a Pulitzer Prize-winning correspondent for "The New York Times" abducted by the Taliban and held for months in Pakistan, reported after his escape in 2009 that he saw the Taliban inflate the number of civilian casualties from U.S. drone strikes in order to make it easier to recruit new fighters.
With agency reports